In this blog entry Tristan Rhodes discuss some of the major advantages that Ubuntu has provided from day one.
Read them here

Quote:

As far as I know, Ubuntu was the first Linux distribution to follow a regular release schedule. Ever since the first version of Ubuntu, Canonical has promised that a new version would be released every 6 months, and that each release would be supported for 18 months. This has proven to be true, except for a 2-month delay to polish the first long-term-support (LTS) release.

We now know that there will be an LTS version of Ubuntu every two years. These LTS versions provide a much longer life-cycle, which is preferred by server administrators. LTS versions receive security updates for 3 years on the Desktop Edition, and 5 years on the Server Edition.